1. Field of the Invention
The present invention relates to airbag modules. More specifically, the present invention relates to a system of deflectable mounting tabs located on an airbag housing to provide good fit and finish between a decorative airbag cover and a vehicle steering wheel.
2. Description of Related Art
Throughout recent decades, airbags have proven to be an effective tool in preventing death and injuries caused by vehicle collisions. In order to provide increased protection for vehicle occupants, airbag modules are currently being employed in multiple locations within a vehicle. Often, airbag modules are placed in highly visible locations of the vehicle, such as the steering wheel or instrument panel. If a highly visible airbag module is not attached properly, the airbag module may have a poor appearance. Attachment problems can result in airbag modules having gaps at their perimeters or not having a flush alignment with adjacent components.
One cause of attachment problems within airbag modules is selecting an appropriate tolerance range for the airbag module components. Generally, airbag module components, as with most components, must balance between tight tolerances and low cost. Tight tolerances are desirable because the attachment fit and size of multiple components are controlled. Tight tolerances also prevent attachable parts from being too large or too small to properly couple corresponding parts. However, obtaining tight tolerances is often very expensive because of the machinery, tools, and materials needed to obtain such tolerances.
While tight tolerances are desirable, processes that are not capable of tight tolerances are commonly employed because of their low cost and short manufacturing time. Processes such as injection molding and metal stamping allow complex components to be manufactured with minimal time and material, resulting in a low cost component. Yet, these processes are not always capable of maintaining tight tolerances. While the inexpensive processes may not have tight tolerances, the tolerances are often within a range that does not cause any attachment or appearance problems.
However, if multiple components having loose tolerances are attached together, the loose tolerances of the individual components may combine to create a product that is out of the overall tolerance range of the part. For example, an airbag module may include an airbag housing made through a stamping process, an airbag cover, and airbag fasteners made by an injection molding processes. Typically, any one of these components may have an acceptable tolerance range. But when all three components are attached together, the overall airbag module may exceed acceptable tolerance ranges. This is known as tolerance stacking.
Tolerance stacking occurs when two or more components are attached to one another where both components are near the extreme allowable tolerances. For example, an airbag housing may have a height of 5 cm±0.2 cm and a airbag cover may have a height of 8 cm±0.3 cm. If both the airbag housing and the airbag cover are at their largest allowable tolerances, the assembled airbag module has a height of 13.5 cm. If both the airbag housing and the airbag cover are at the lowest allowable tolerances, the assembled airbag has a height of 12.5 cm. The difference between the largest and smallest assembled airbag modules is ±0.5 cm. Thus, the tolerances of two objects may have a tolerance range that is outside the allowable range of any one of the individual components.
In an airbag module, the airbag cover is generally attached to the airbag housing, creating the potential for tolerance stacking between the two components. Additionally, the airbag housing may be attached to a vehicle structural member through injection molded fasteners, possibly creating additional tolerance stacking. If all three of the components are at their high end of allowable tolerances, the airbag module may extend above adjacent components and may also have a gap around its perimeter. If all three components are at their low end of allowable tolerances, the airbag module may be recessed too far into the vehicle attachment structure.
Thus, the cost and fit of an airbag module are often weighed against each other. If the tolerances on the airbag module components are tight, the airbag module will have a proper fit, but the overall cost of the airbag module will be high. Alternatively, if the tolerances of the airbag module components are loose, the overall cost of the airbag module will be low, but may have a poor fit.
Therefore, what is needed in the art is an airbag module capable of a properly aligned fit within a vehicle. What is also needed in the art is an airbag module that may be manufactured using inexpensive processes. What is further needed is a system for inexpensively correcting the result of tolerance stacking in an airbag module. Such a system and apparatus is disclosed herein.